Final answer:
The phrase suggests that as day ends, it becomes enveloped by evening mists, symbolizing a natural transition to night.
Step-by-step explanation:
The phrase "wrapping the mists round her withering form" in the last stanza of "March Evening" suggests a metaphorical representation of the transition from day to night. The personification of 'daytime' as weary and succumbing to the enveloping mists and inevitable arrival of evening reflects a natural, cyclical change. It implies that the day is coming to an end, giving way to the night which is cloaking the world in mists and darkness.
The phrase 'wrapping the mists round her withering form' in the last stanza of 'march evening' suggests that the day is trying to protect itself from the evening by cloaking itself against the rain. It conveys the imagery of the evening drizzle enveloping the daytime as it comes to an end, symbolizing the transition from day to night.